Why Do Some Recordings Sound Great and Others Dead?

For what its worth, I use an Analog Production vinyl pressing of Nora Jones' 1st lp to show off my system to friends. Sounds great! So the original recording is very good. Not sure if this helps as a reference for streaming this recording.

i've noticed there is a wide variety in sound quality from recording to recording, even those made in the same studio with the same people. a lot can go wrong between the studio and your listening room, at multiple steps along the way. some recording studios [particularly classical labels] try to ameliorate this situation by using consumer equipment in a consumer-type of studio listening room, to make their sound something that sounds more reasonable in a typical home listening environment. i have found that for most situations, a certain modest amount of dynamic range compression/limiting is helpful to make a given recording sound the best in the universe of different listening environments/equipment complements out there. there is an artful way of doing this which doesn't do [as much] dirt to the lucky owners of megabuck equipment and megabuck listening rooms. a light touch is required, but not all recording professionals have a light touch, as witnessed by the thousand and one sins one hears in commercial recordings. the biggest sin IMHO is mixing the vocals in a way that they are barely discernible from the musical background, i believe the germ of this idea came from hollywood movies with their emphasis on "realism" IOW maximizing the [relative] impact of the loud parts by reducing the volume/clarity of dialogue. a lot of artists don't care to have their vocals too high in the mix [Elvis was a notable example], and the engineers are all too happy to play along. i have [per audiological exam/spectrogram] normal hearing for my age, so when i hear muffled vocals listening on my Sennheiser HD580 cans, i know something is wrong with the recording. 

@erik_squires  Thx for your explanation.  I reread it, and I can appreciate the considerable time and expertise in your analysis.  I don’t currently have enough knowledge to follow up on it with any confidence. My room is a mess, but I  can’t do much to improve it.  I tried following various suggestions and acoustic placement principles, but with 2 Beolab8000 speakers, 2 subs and an unwieldy room, I’m just guessing.  I’ve worked on speaker microadjustments,  Next I’ll try the subs.  Since my speakers and subs are all powered, I’m not using a preamp with the SMSL M400.  I wonder if that could be a problem? Maybe some day I’ll have more confidence to try minidsp or Dirac.

@emrofsemanon  Thx for your comments!  I just listened to May Erlewine’s ‘Days Gone By’ and her voice was very forward, loud and clear.  I believe the same is true of the Nora Jones recording mentioned above - but it just does not come through on my stereo system.  Until I get it ‘fixed’ I’ll just listen to what sounds best for me. 

@OP - If you feel uncomfortable, here's my recommendation:

Corner Bass traps or soffit traps from GIK.   The soffit traps work a little better, but the corner bass traps give you more floor space.

Not sure if RP is the a good reference or not as I don't use that service, but there are a couple things to consider. 

- If you don't know the CAT # of the specific album, well that is a major prob.  That is also a big downside to streaming - you have no idea (many times) of the provenance as well as they can remove/change said album version at any given point and you'll never know (generally speaking)

- The recording/mixing/mastering means everything (provenance) and if one doesn't know that then all bets are off

- Some recordings most def sound better than others (I would hope so)?  However, as has been pointed out, the room/acoustics are paramount to SQ along with proper setup.  Those two items are an absolute MUST before anything else.